BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a work mounting device, for mounting a work on a
work mounting member using a robot, and, in particular, it relates to a work mounting
device that can be utilized for teaching the attitude of a hand to mount the work
properly.
2. Description of the Related Art
[0002] Conventionally, in order to create a robot program to allow a robot to handle a work
and mount it on a work mounting member, which is provided with a plurality of work
support sections, it is necessary to teach the position and attitude when the work
is mounted while, first, moving a hand installed in the robot up to the proximity
of the work support sections of the work mounting member by manually feeding the robot
and, then, fine-tuning the attitude of the hand by manual feeding of the robot so
that the work comes into uniform contact with all the work support sections.
[0003] Thus, this adjustment operation, to repeat one trial and error operation after another,
is usually very cumbersome and, in particular, when the work is large, it is burdensome
even for experts and, further, it is very difficult for nonexperts to perform this
operation. Therefore, it is a major cause of an increase in time for teaching the
program to the robot. Nevertheless, the fact of the matter is that no suitable method
to solve the difficulties in teaching has been developed.
[0004] In this connection, though no publicly-known literature similar to the present invention
has been found, a well-known disturbance observer, that is utilized for detecting
contact between the work and the work mounting member as described below, is described,
for example, in United States Patent 5,304,906 issued on April 19, 1994 to Arita,
et al. and United States Patent 5,936,369 issued on August 10, 1999 to Iwashita, et
al.
SUMMARY OF THE INVENTION
[0005] In view of the above problem, it is an object of the present invention to provide
a work mounting device that is useful for performing a teaching operation simply,
and in a short time, to allow a robot to handle a work and mount it on a work mounting
member. Further, through the provision of such work mounting device, the present invention
reduces the time for teaching the robot and, thus, the burden on an operator so that
even nonexperts can perform teaching tasks easily.
[0006] The present invention solves the above problems by automating an adjustment operation,
which is conventionally performed by manual feeding to repeated trial and error operations
as described above, by means of a method for controlling attitude of a hand using
distance information obtained by distance measuring means disposed at a plurality
of positions on the work mounting member or on a work holding section, that is, the
hand (or, in other words, by means of a robot attitude controller). More specifically,
the present invention is applied to a device that holds a work by a work holding section
or a hand, which is installed in a robot controlled by a robot controller, and mounts
the held work on the work mounting member. The present invention may have various
aspects as follows:
[0007] A work mounting device according to a basic aspect of the present invention comprises:
a work holding section for holding a work; a work mounting member for mounting said
work thereon, which has a plurality of contacting regions that come into contact with
a plurality of contacting regions on said work separately when said work is mounted
thereon; a plurality of distance measuring devices, each of which has a measurement
reference point and which provide a plurality of distance data representing distances
between said work held by said work holding section and said work mounting member
based on each of said measurement reference points; a storage section for storing
said plurality of distance data provided by said plurality of distance measuring devices;
a driving mechanism for moving said work holding section so that said work held by
said work holding section approaches said work mounting member; and an attitude control
section that, while said work holding section is operating, controls said driving
mechanism to adjust the attitude of said work holding section based on said plurality
of distance data stored in said storage section so that distances between said contacting
regions of said work and said work mounting member, which are to eventually come into
contact with each other, are maintained uniformly and, on the other hand, stops the
movement of said work holding section when a predetermined condition is satisfied
while said attitude is being adjusted.
[0008] Here, the plurality of distance measuring devices are provided at a plurality of
locations on the work mounting member and the devices measure the minimum distances
between each measurement reference point and the work. Preferably, the plurality of
distance measuring devices are disposed in the contacting regions of the work mounting
member.
[0009] Alternatively, the plurality of distance measuring devices may be provided at a plurality
of locations on the work holding section and the devices may measure the minimum distances
between each measurement reference point and the work mounting member.
[0010] Here, the predetermined condition may be determined as a condition concerning the
distance between the work and the work mounting member and, more specifically, it
may be determined based on a difference between an evaluation index indicating how
close the work and the work mounting member are to each other and a predetermined
threshold for such evaluation index. Alternatively, the predetermined condition may
be determined based on whether contact between the work and the work mounting member
is detected or not. In this case, the presence or absence of the contact can be determined,
for example, based on a disturbance estimation observer provided in the attitude control
section or, by detecting variation of load on the driving mechanism, it can be determined
based on the detection result.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The above and other objects, features and advantages of the present invention will
be made more apparent, from the following description of the preferred embodiments
thereof, with reference to the accompanying drawings, wherein:
Fig. 1 is a block diagram for describing a schematic configuration of a work mounting
device of the present invention;
Fig. 2 is a block diagram for describing a schematic configuration of a preferred
embodiment of the work mounting device of the present invention;
Fig. 3 is an outline diagram showing how a work gripped by a hand and a work mounting
member are disposed in an embodiment in which distance sensors are mounted on the
side of the work mounting member;
Fig. 4 is an outline diagram showing how the work gripped by the hand and the work
mounting member are disposed in an embodiment in which the distance sensors are mounted
on the side of the hand;
Fig. 5 is the first half of a flow chart showing a schematic process for controlling
a final approaching/mounting operation; and
Fig. 6 is the second half of the flow chart showing the schematic process for controlling
the final approaching/mounting operation.
DETAILED DESCRIPTION
[0012] Fig. 1 is a block diagram for describing a schematic configuration of a work mounting
device of the present invention and Fig. 2 is a block diagram for describing a schematic
configuration of a preferred embodiment of the work mounting device of the present
invention.
[0013] As shown in Fig. 1, a work mounting device comprises: a work holding section for
holding a work; a work mounting member for mounting said work thereon, which has a
plurality of contacting regions that come into contact with a plurality of contacting
regions on said work separately when said work is mounted thereon; a plurality of
distance measuring devices, each of which has a measurement reference point and which
provide a plurality of distance data representing distances between said work held
by said work holding section and said work mounting member based on each of said measurement
reference points; a storage section for storing said plurality of distance data provided
by said plurality of distance measuring devices; a driving mechanism for moving said
work holding section so that said work held by said work holding section approaches
said work mounting member; and an attitude control section that, while said work holding
section is operating, controls said driving mechanism to adjust the attitude of said
work holding section based on said plurality of distance data stored in said storage
section so that distances between said contacting regions of said work and said work
mounting member, which are to eventually come into contact with each other, are maintained
uniformly and, on the other hand, stops the movement of said work holding section
when a predetermined condition is satisfied while said attitude is being adjusted.
[0014] An embodiment of the work mounting device shown in Fig. 2 is comprised of: a robot
(a mechanism section) 10 equipped with a work holding section or hand (not shown in
Fig. 2; see Fig. 3 or 4 described below); a teaching control panel 30; a number of
(three in the shown example) distance measuring devices or distance sensors 1 - 3;
and an attitude control section or a robot controller 20 connected to these elements.
The robot controller 20 does not particularly differ from a typical robot system except
that the robot controller 20 is connected to the distance sensors 1 - 3 via an interface
for the sensors (not shown) and that the robot controller 20 is equipped with software
for performing a process shown in a flow chart of Figs. 5 and 6 described below by
using data obtained by the distance sensors 1 - 3.
[0015] Further, the robot controller 20, in a well-known manner, comprises a disturbance
estimation observer for a speed loop of servomotor (driving mechanism) control of
each robot axis that can estimate and output a disturbance torque according to a torque
command and an actual speed. A disturbance estimation observer that can be used in
the present invention has been described, for example, in United States Patent 5,304,906
issued on April 19, 1994 to Arita, et al. and United States Patent 5,936,369 on August
10, 1999 to Iwashita, et al., the disclosure of which is incorporated herein by reference.
Alternatively, in place of the disturbance estimation observer, a current values to
the motor of each axis may be monitored and output.
[0016] The teaching control panel 30 is connected to the robot controller 20 via an interface
for the teaching control panel in a typical manner and provided with: a display 31,
a jog key (manual feed key) 32, a teaching key 33 and an approaching key 34. As well
known, the jog key (manual feed key) 32 allows the robot 10 to perform translational
or rotational motion specified by the operator gradually. The teaching key 33 is a
key for storing current position coordinates (x, y, z, p, w, r) (x, y and z are related
to the translational motion and p, w and r are related to the rotational motion) in
a storage section or memory in the robot controller 20 by pushing it down when the
robot is positioned and stopped. Further, the approaching key 34 provides a means
for manually inputting commands to start and continue the process shown in the flow
chart of Figs. 5 and 6 described below. In this connection, in addition to these functions
by means of the keys, the teaching control panel 30 is further provided with means
for editing and modifying programs, setting various parameters and performing an emergency
stop. Further, the teaching control panel 30 may optionally be provided with features
for capturing data on distances measured by the distance sensors 1 - 3 and displaying
the data on the display 31.
[0017] Next, Figs. 3 and 4 are outline diagrams showing how a work gripped by a hand and
a work mounting member in the work mounting device, which is schematically shown in
Fig. 2, are disposed in two cases in which the distance sensors are mounted at different
positions from each other, wherein Fig. 3 shows the case in which the distance sensors
are mounted on the side of the work mounting member and Fig. 4 shows the case in which
the distance sensors are mounted on the side of the hand. In these figures, a reference
numeral 11 designates an arm tip portion of the robot 10, on which the hand 12 is
placed. The hand 12 grips the work 50 as shown and, in this embodiment, an operation
for teaching the robot to mount the work 50 on the work mounting member 60 is considered.
[0018] The work 50 shown in this example is provided with holes 51 - 53 that are formed
at three corners thereof and the work mounting member 60 is provided with protrusions
61 - 63 that are formed at positions precisely corresponding to the holes 51 - 53.
Therefore, a region around the hole 51 and the protrusion 61, a region around the
hole 52 and the protrusion 62, and a region around the hole 53 and the protrusion
63, respectively, correspond and eventually make contact with each other.
[0019] The positions of the distance sensors 1 - 3 on the work mounting member 60 or the
hand 12 are selected so that they are not in line with one another. Further, when
the distance sensors 1 - 3 are mounted on the work mounting member 60, the distance
sensors 1 - 3 are preferably, but not necessarily, placed in regions that correspond
and eventually make contact with the work (in the neighborhood of the protrusions
61 - 63 in this example), as shown in Fig. 3. Still further, when the distance sensors
1 - 3 are mounted on the hand 12, the distance sensors 1 - 3 are preferably, but not
necessarily, placed in the neighborhood of the contact points where the work is gripped,
as shown in Fig. 4.
[0020] Hereinafter, a procedure for teaching a mounting operation on the work mounting member
60 by using the work mounting device shown in Figs. 2 and 3 or in Figs. 2 and 4. Here,
for convenience, it is assumed that the robot 10 grips the work 50 by the hand 12
and resides in a position somewhat apart from the work mounting member 60 (out of
measurement range of the distance sensors 1 - 3) in its initial state.
(1) Preliminary approach
[0021] First, the operator manipulates the jog key 32 of the teaching control panel 30 to
move the robot 10 so that the work 50 is located in the neighborhood of a position
substantially directly above the work mounting member 60, as shown in Fig. 3 or 4.
For convenience, this movement is referred to as a preliminary approach. The hand
12 (the robot 10) preferably takes an attitude substantially same as the eventual
attitude to mount the work 50. In this example, this attitude corresponds to a state
in which distances between the holes 51 - 53 and the corresponding protrusions 61
- 63 are substantially equal to one another.
[0022] In this connection, the operation for this preliminary approach may be performed
by executing a program that has been created in advance. Further, in order to check
whether the preliminary approach has been performed properly, measurement values of
the distance sensors 1 - 3 are preferably displayed on the display 31 in this step
so as to check whether each distance sensor 1 - 3 can measure the distance between
itself and the work 50 (in the case of Fig. 3) or the distance between itself and
the work mounting member 60 (in the case of Fig. 4) and whether the measurement values
of the distance sensors 1 - 3 are reasonable values that do not differ from one another
too much (for example, each measurement value falls within ± 20 % of the average measurement
values). If the measurement values differ from one another too much or the values
cannot be measured, a measure such as readjustment of the preliminarily approached
position must be taken.
(2) Final approach/mounting operation
[0023] After the preliminary approach is completed, an operation is performed to allow the
work 50 to approach the work mounting member 60 to reach a position where the work
50 is mounted on or is very close to being mounted on the work mounting member 60.
For convenience, this operation is referred to as a final approach/mounting operation.
Conventionally, this operation has been performed through an adjustment operation
in which the operator manually feeds the work 50 (or manipulates the jog key 32) to
allow the work 50 to approach the work mounting member 60 while keeping the work 50
parallel to the work mounting member 60 (at this time, all the measurement values
of each sensor are equal to one another). As described above, this adjustment operation
was not easy even for experts but, in this embodiment, it can be performed automatically
only by pushing down the approaching key 34 of the teaching control panel 30.
[0024] More specifically, once the approaching key 34 is pushed down, the robot controller
20 controls the position and the attitude of the robot 10 to allow the work 50 to
approach the work mounting member 60 while maintaining a proper attitudinal relationship
(a parallel relationship in this example) between the work 50 and the work mounting
member 60. Figs. 5 and 6 are a flow chart showing a schematic process for this control,
wherein Fig. 5 is the first half showing steps that are mainly related to attitude
control (control of attitudes in relation to a tool coordinate system) and Fig. 6
is the second half showing steps that are mainly related to position control (translational
motion of a tool tip point). A basically identical algorithm is used in either of
Figs. 3 and 4 and, therefore, the case in which the distance sensors are attached
to the work mounting member (Fig. 3) will be described here. The main points of each
step are as follows:
Step S1: Set an index m for the attitude control and an index n for the position control
described below to initial values (m = n = 1).
Step S2: Store current position coordinates (the position when the preliminary approach
described above is completed) as standard position coordinates.
Step S3: Move the robot to the m-th attitude adjustment positions. Here, the "m-th
attitude adjustment positions" are determined as follows:
(a) the 1st attitude adjustment position is the standard position itself. Therefore,
only when m = 1, this step S3 is skipped but, at this time, a startup command specifying
that "movement is zero" is output;
(b) the 2nd attitude adjustment position (m = 2) is a position that is rotated from
the standard position about the X-axis of the tool coordinate system by a predetermined
very small angle (Δw). Assuming that the attitude components of the standard position
are (wst, pst, ret), the attitude components of this 2nd attitude adjustment position are (wst + Δw, pst, ret);
(c) the 3rd attitude adjustment position (m = 3) is a position that is rotated about
the Y-axis of the tool coordinate system by a predetermined very small angle (Δp)
(wst, pet + Δp, rst);
(d) the 4th attitude adjustment position (m = 4) is a position that is rotated about
the Z-axis of the tool coordinate system by a predetermined very small angle (Δr)
(wst, pst, rst + Δr); and
(e) the 5th attitude adjustment position (m = 5) is a position that is rotated about
the X-axis of the tool coordinate system by an angle twice as large as the predetermined
very small angle Δw (2Δw) (wst + 2Δw, pst, rst).
Hereinafter, in a similar manner, assuming a positive integer g in advance and,
then, adjustment attitudes (w
et + iΔw, p
et + jΔp, r
et + kΔr) corresponding to all combinations (i, j, k), where -g ≤ i ≤ g, -g ≤ j ≤ g,
-g ≤ k ≤ g (i, j, k are integers), are generated by labeling m in a one-to-one relationship.
The total number of the generated adjustment attitudes is (2g)
3 and the maximum value M of the index m is M = (2g)
3 + 1.
In this connection, if a signal indicating that the work 50 is in contact with
the work mounting member 60 is output during the movement in step S3, the robot is
stopped urgently. For example, if the disturbance torque estimated by the disturbance
estimation observer described above or monitored current values of each axis exceed
predetermined upper limit values, the robot is stopped urgently.
Step S4: In every attitude taken in step S3, load outputs of each distance sensor
into the robot controller 20 to collect measured distance data ll - lf. Here, the
number of the sensors is f = 3 and, therefore, 3 items of the distance data are collected
and the data for each sensor is stored by labeling with the corresponding indices
m.
Step S5: Calculate evaluation indices L for checking appropriateness of the attitudes.
For example, L is calculated by the following equation (1):

(where the subscripts a and b indicate that la and lb are measurement values by the a-th distance sensor and the b-th distance sensor different
from the a-th sensor, respectively, and the summation Σ should be taken for all combinations
of 1 ≤ a ≤ f and 1 ≤ b ≤ f).
If f = 3, the above equation (1) takes the following form:

The calculated values L are stored by labeling with the indices m.
Step S6: Check whether the steps S3 - S5 are completed for all the adjustment attitudes.
If not completed, the process proceeds to step S7 or, if completed, the process proceeds
to step S9.
Step S7: Check whether the approaching key 34 (see Fig. 2) is being pushed down. If
it is being pushed down, the process proceeds to step S8 or, if it is not being pushed
down, the process terminates. Thus, the operator can select to terminate/continue
the approaching/mounting operation at any time.
Step S8: Add 1 to the attitude adjustment index m and return to step S3.
Step S9: Determine the minimum L = Lmin.
Step S10/step S11: Move the robot to the attitude corresponding to the index m giving
the minimum L =Lmin. At this point in time, it can be considered that the attitude adjustment for 1 cycle
is completed. But, in order to ascertain that the attitude adjustment satisfies minimum
appropriateness, the process proceeds to step S11. An acceptable upper limit value
Q is determined for Lmin in advance. If Lmin < Q, the process proceeds to step S12 or, otherwise, the process returns to step
S1 and, then, step S2 and the subsequent steps are repeated to readjust the attitude.
Here, it is to be noted that the "current position" in step S2 at this time is the
position to which the robot has been moved in the preceding step S10. Thus, the "standard
attitude" for the next cycle is an attitude at least after a certain attitude adjustment
has been performed though it did not pass the step S11. Therefore, it can be expected
with a high probability that the attitude of the robot will pass step S11 after a
number of trials.
Step S12: Calculate an evaluation index L0 for checking how the work 50 approaches the work mounting member 60 with regard to
the index m giving Lmin. L0 can be calculated by the following equation (3):

If f = 3, the above equation (3) takes the following form:

Step S13: Compare L0 with a predetermined threshold R for the evaluation index L0 and, if L0 is not more than R, terminate the approaching/mounting operation. Further, indicate
the result on the display 31. After recognizing the result, the operator releases
the approaching key 34 and pushes the teaching key 33 down to teach the current position.
If L0 > R, the process proceeds to step SS1 (the process moves into the flow chart of Fig.
6 from the reference numeral A). In this connection, the value R is preferably set
to be equal to or slightly larger than a value of L0 obtained when all the holes 51 - 53 of the work 50 are engaged with the protrusions
61 - 63 and the work 50 is mounted on the work mounting member 60 completely.
Step SS1: Store the current position (the position when step S12 is completed) as
the standard position.
Step SS2: Move the robot to the n-th translational adjustment positions. Here, the
"n-th translational adjustment positions" are determined as follows:
(a) the 1st translational adjustment position (n = 1) is a position to which the tool
tip point is translated from the standard position in the direction of the X-axis
by a predetermined very small distance (Δx). Assuming that the positional components
of the standard position are (xst, yst, zst), the positional components of this 1st translational adjustment position are (xst + Δx, yst, zst);
(b) the 2nd translational adjustment position (n = 2) is a position to which the tool
tip point is translated from the standard position in the direction of the Y-axis
by a predetermined very small distance (Δy) (xst, yst + Δy, zst);
(c) the 3rd translational adjustment position (n = 3) is a position to which the tool
tip point is translated from the standard position in the direction of the Z-axis
by a predetermined very small distance (Δz) (xst, yst, zst + Δz);
(d) the 4th translational adjustment position (n = 4) is a position to which the tool
tip point is translated from the standard position in the direction of the X-axis
by a distance twice as large as the predetermined very small distance (Δx) (xst + 2Δx, yst, zst); and
(e) hereinafter, in a similar manner, assuming a positive integer h in advance and,
then adjustment positions (xst + iΔx, yst + jΔy, zst + kΔz) corresponding to all combinations (i, j, k), where -h ≤ i ≤ h, -h ≤ j ≤ h,
-h ≤ k ≤ h, are generated by labeling n in a one-to-one relationship. The total number
of the generated adjustment attitudes is (2h)3 and the maximum value N of the index n is N = (2h)3.
In this connection, if a signal indicating that the work 50 is in contact with
the work mounting member 60 is output during the movement in step SS2, the robot is
stopped urgently in a similar manner to the case in step S3 described above.
Step SS3: In every position taken in step SS2, load outputs of each distance sensor
into the robot controller 20 to collect measured distance data ll - lf. Here, the
number of the sensors is f = 3 and, therefore, 3 items of the distance data are collected
and the data for each sensor is stored by labeling with the corresponding indices
n.
Step SS4: Calculate evaluation indices LL for checking uniformity of the approach.
LL can be calculated by the same equation as the equation (1) or (2) described above,
for example. The calculated value LL is stored by labeling with the indices n.
Step SS5: Check whether the steps SS2 - SS4 are completed for all the translational
adjustment positions. If not completed, the process proceeds to step SS6 or, if completed,
the process proceeds to step SS8.
Step SS6: Check whether the approaching key (see Fig. 2) is being pushed down. If
it is being pushed down, the process proceeds to step SS7 or, if it is not being pushed
down, the process terminates. Thus, the operator can select to terminate/continue
the approaching/mounting operation at any time.
Step SS7: Add 1 to the translational adjustment index n and return to step SS2.
Step SS8: Determine the minimum LL = LLmin.
Step SS9/Step SS10: Move the robot to the position corresponding to the index n giving
the minimum L = Lmin. At this point in time, it can be considered that the translational position adjustment
for 1 cycle is completed. Here, in order to ascertain that the uniformity of the approach
satisfies minimum requirements, the process proceeds to step SS10. An acceptable upper
limit value Q is determined for LLmin in advance. Here, the same value as the upper limit value of Lmin used in step S11 is adopted. If LLmin < Q, the process proceeds to step SS11 or, otherwise, the process returns to step
S1 and, then, step S2 and the subsequent steps are repeated to readjust the attitude
(the process moves into the flow chart of Fig. 5 from the reference numeral B). But,
here, it is to be noted that the "current position" in step S2 at this time is the
position to which the robot has been moved in the preceding step SS9.
Step SS11: Calculate the evaluation index L0 for checking how the work 50 approaches the work mounting member 60 with regard to
the index n giving Lmin. L0 can be calculated by the equation (3) or (4) set forth above.
Step SS12: Compare L0 with the predetermined threshold R and, if L0 is not more than R, terminate the approaching/mounting operation. Further, indicate
the result on the display 31. After recognizing the result, the operator releases
the approaching key 34 and pushes the teaching key 33 down to teach the current position.
If L0 > R, step SS1 and the subsequent steps are performed again. At this time, the "current
position" in step SS2 is the position to which the robot has been moved in the preceding
step SS9. Therefore, it can be expected with a high probability that the position
of the robot will pass the step S11 after a number of trials.
[0025] As described above, the operator can teach the robot an appropriate position and
attitude to allow the work 50 to approach the work mounting member 60 uniformly and
to be mounted thereon only by pushing the approaching key 34 down continuously for
an adequate time period (till the display 31 indicates that the approaching/mounting
operation is completed).
[0026] In this connection, though distance information is used as the reference to decide
to stop the robot, other information may be used. For example, the disturbance estimation
observer described above may be used for detecting the completion of the approaching/mounting
operation of the work 50 onto the work mounting member 60 to terminate the approaching/mounting
operation. More specifically, as described above, the disturbance estimation observer
may be configured with regard to a speed loop of servomotor control of the robot so
that a disturbance torque can be estimated based on a torque command and an actual
speed and, if the magnitude of the estimated disturbance torque exceeds a predetermined
value, it may be considered that the work 50 is in contact with the work mounting
member 60 and the approaching/mounting operation may be terminated. Alternatively,
current values of motors for each axis may be monitored and, if the values exceed
a predetermined value, it may be considered that the work 50 is in contact with the
work mounting member 60 and the approaching/mounting operation may be terminated.
[0027] As described above, in this application, as a plurality of distance measuring means
are disposed on the work mounting member or the hand, a positional relationship between
the work mounting member and the work can be known based on the distance information
obtained thereby and the attitude of the hand (the attitude of the robot) can be controlled
automatically so that corresponding contacting regions of the work and the work mounting
member approach each other immediately before contact uniformly and the robot can
be stopped when it is determined that the adequate approach or contact occurs based
on the distance data, the disturbance estimation observer, the load torque and the
like. Therefore, most of cumbersome tasks that have been required of the operator
conventionally become unnecessary. Thus, when the work mounting device of the present
invention is utilized, the manual feeding operation of the robot that is required
of the operator may be only a simple operation to allow the corresponding contacting
regions of the work and the work mounting member to approach each other within a certain
distance range (an effective measuring range of the distance sensors).
[0028] After such a rough approach is completed, the operator can move the work toward support
sections of the work mounting member automatically through key manipulation and the
like. During this movement, the robot controller determines the distances between
each support section and the work continuously from the data output from the distance
measuring means and controls the attitude of the hand of the robot so that the distances
between each support section (each corresponding contacting region) and the work are
reduced uniformly. Finally, the movement is stopped when any contact is detected.
As the attitude of the hand at this point in time is equivalent to the one that the
experts determined finally after time-consuming trial and error by manual feeding
in the prior art, the result of the present invention is that the teaching operation
has become easy for experts and nonexperts alike. In this connection, various distance
measuring devices such as a laser distance sensor, an ultrasonic distance sensor,
an optical distance sensor using infrared light and a stereographic sensor using two
cameras are well-known and can be adopted as appropriate.
[0029] According to the present invention, in a robot for handling a work, attitude adjustment
of a hand can be automated when the work is mounted on a work mounting member. Therefore,
the time for teaching the robot and, thus, the burden on the operator, can be reduced.
Further, even nonexperts can perform teaching tasks easily.
[0030] While the invention has been described with reference to specific embodiments chosen
for the purpose of illustration, it should be apparent that numerous modifications
could be made thereto, by one skilled in the art, without departing from the basic
concept and scope of the invention.